A phased array antenna uses multiple radiating elements to transmit, receive, or transmit and receive radio frequency (RF) signals. Phased array antennas are used in various capacities, including communications on the move (COTM) antennas, satellite communication (SATCOM) airborne terminals, SATCOM mobile communications, and SATCOM earth terminals. The application of mobile terminals typically requires the use of automatic tracking antennas that are able to steer the beam in azimuth, elevation, and polarization to follow the satellite position while the vehicle is in motion.
One well known type of phased array antenna is an electronically steerable phased array antenna. The electronically steerable phased array antenna has full electronic steering capability and is more compact and lower profile than a comparable mechanical phased array antenna. The main drawback of fully electronic steering is that the antenna usually requires the integration of a lot of expensive analog RF electronic components which may prohibitively raise the cost for commercial applications. A typical electronically steerable phased array antenna comprises an assembly of phase shifters, power splitters, power combiners, and quadrature hybrids. Additionally, a typical electronically steerable phased array requires at least a few of these components at every element in the phased array, which increases the cost and complexity of the architecture.
Phase shifters are used in a phased array antenna in order to steer the beam of the signals by controlling the respective phases of the RF signals communicated through the phase shifters. A typical digital phase shifter uses switched delay lines, is physically large, and operates over a narrow band of frequencies due to its distributed nature. Another typical digital phase shifter implements a switched high-pass low-pass filter architecture which has better operating bandwidth compared to a switched delay line but is still physically large.
Also, the phase shifter is often made on gallium arsenide (GaAs). Though other materials may be used, GaAs is a higher quality material designed and controlled to provide good performance of electronic devices. However, in addition to being a higher quality material than the other possible materials, GaAs is also more expensive and more difficult to manufacture. The typical phased array components take up a lot of area on the GaAs, and result in higher costs. Furthermore, a standard phase shifter has high RF loss, which is typically about n+1 dB of loss, where n is the number of phase bits in the phase shifter. Another prior art embodiment uses RF MEMS switches and has lower loss but still consumes similar space and is incompatible with monolithic solutions.